U.S. patent number 5,426,219 [Application Number 08/096,939] was granted by the patent office on 1995-06-20 for process for recovering organic acids.
This patent grant is currently assigned to A.E. Staley Manufacturing Co.. Invention is credited to William F. Lehnhardt, Lori L. Napier, Robert V. Schanefelt.
United States Patent |
5,426,219 |
Lehnhardt , et al. |
June 20, 1995 |
**Please see images for:
( Certificate of Correction ) ** |
Process for recovering organic acids
Abstract
An organic acid can be recovered from a fermentation broth by
clarifying the broth to remove at least a substantial portion of
the impurities therein, producing a clarified feed; acidulating the
clarified feed by adding a quantity of a mineral acid effective to
lower the pH of the feed to between about 1.0 and about 4.5,
producing an acidulated feed which is substantially saturated with
respect to at least one electrolyte selected from the group
consisting of MHSO.sub.4, M.sub.2 SO.sub.4, M.sub.3 PO.sub.4,
M.sub.2 HPO.sub.4, MH.sub.2 PO.sub.4, and MNO.sub.3, where M is
selected from the group consisting of Na, NH.sub.4, and K;
extracting the acidulated feed with an extraction mixture which
includes (a) water, (b) a mineral acid, in a quantity effective to
maintain the pH of the feed between about 1.0 and about 4.5, and
(c) an oxygenated solvent which has limited miscibility with water
and the acidulated feed, the oxygenated solvent having from 4 to 12
carbon atoms and having at least one functional group selected from
the group consisting of hydroxyl, ester, keto, ether, carbonyl, and
amido, with the extraction producing a solvent extract and a first
raffinate; and back extracting the solvent extract with an aqueous
liquid, thereby producing an organic acid-rich aqueous extract and
an organic acid-depleted solvent raffinate.
Inventors: |
Lehnhardt; William F. (Decatur,
IL), Schanefelt; Robert V. (Decatur, IL), Napier; Lori
L. (Decatur, IL) |
Assignee: |
A.E. Staley Manufacturing Co.
(Decatur, IL)
|
Family
ID: |
22259836 |
Appl.
No.: |
08/096,939 |
Filed: |
July 26, 1993 |
Current U.S.
Class: |
562/580; 562/578;
562/589; 562/593 |
Current CPC
Class: |
C07C
51/48 (20130101); C12P 7/56 (20130101); C07C
51/48 (20130101); C07C 59/08 (20130101) |
Current International
Class: |
C07C
51/42 (20060101); C07C 51/48 (20060101); C12P
7/40 (20060101); C12P 7/56 (20060101); C07C
051/42 () |
Field of
Search: |
;562/580,589,578,593 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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0375463 |
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Dec 1989 |
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EP |
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0393818 |
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Feb 1990 |
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EP |
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0517242 |
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Dec 1992 |
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EP |
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WO93/00440 |
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Jan 1993 |
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WO |
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WO93/06226 |
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Apr 1993 |
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WO |
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Other References
Dietz et al, "Physical Properties of Sodium, Potassium, and
Ammonium Lactate Solutions," Industrial and Engineering Chemistry,
33:11, pp. 1444-1447 (Nov. 1941). .
Pan et al, "Purification of Lactic Acid for Fermentation of Corn
Products," Chemical Abstracts 113:96160c (1990). .
Czytko et al, "Continuous Glucose Fermentation for Lactic Acid
Production Recovery of Acid by Electrodialysis," Chemical Abstracts
112:117239g (1990). .
Eveleva et al, "Lactic Acid," Chemical Abstracts 111:132518v
(1989). .
Obara, "Purfication of Lactic Acid from Fermentation Broth,"
Chemical Abstracts 111:76553p (1989). .
Obara, "Purification of Organic Acid from Fermentation Fluid and
Apparatus Therefor," Chemical Abstracts 111:22197g (1989). .
Ono et al, "Separation of Lactic Acid by Extraction with Isopropyl
Acetate," Chemical Abstracts 110:172707s (1989). .
Maenato et al, "Separation and Purification of Lactic Acid,"
Chemical Abstracts 107:115250b (1987). .
Daicel Chemical Industries, Ltd., "Purification of Lactic Acid,"
Chemical Abstracts 95:203332u (1981). .
Griffith et al, "Continuous Lactic Acid Production Using a
Fixed-Film System," Chemical Abstracts 92:58182b (1980). .
Napierala et al, "Production of Alimentary Lactic Acid of High
Purity," Chemical Abstracts 78:135586b (1973). .
Vogt et al, "Continuous Recovery of Pure Lactic Acid," Chemical
Abstracts 75:117972h (1971). .
Chaintron, "Purification of Lactic Acid," Chemical Abstracts
74:41925b (1971). .
Boroda et al, "Purification and Concentration of Lactic Acid,"
Chemical Abstracts 70:67528s (1969). .
Colin et al, "Extraction of Organic Acids," Chemical Abstracts
69:42459y (1968). .
Robatel Inc. proposal (Mar. 3, 1993). .
Ono, "Purification of lactic acid with activated carbon," Chemical
Abstacts 110:74833k (1989)..
|
Primary Examiner: Dees; Jose G.
Assistant Examiner: Frazier; Barbara S.
Attorney, Agent or Firm: Arnold, White & Durkee
Claims
We claim:
1. A process for the extraction of an organic acid from an aqueous
solution thereof which comprises contacting an aqueous solution of
an organic acid, wherein the organic acid is selected from the
group consisting of mono, di, and tricarboxylic acids having from
3-8 carbon atoms, with a mixture consisting essentially of (a)
water, (b) a mineral acid in a quantity effective to maintain the
pH of the mixture between about 1.0 and about 4.5, and (c) an
oxygenated solvent which has limited miscibility with water and the
aqueous solution, the oxygenated solvent having from 6 to 8 carbon
atoms and having at least one functional group selected from the
group consisting of hydroxyl, ester, keto, ether, carbonyl, and
amido.
2. The process of claim 1, where the aqueous solution of organic
acid is substantially saturated with respect to at least one
electrolyte selected from the group consisting of MHSO.sub.4,
M.sub.2 SO.sub.4, M.sub.3 PO.sub.4, M.sub.2 HPO.sub.4, MH.sub.2
PO.sub.4, and MNO.sub.3, where M is selected from the group
consisting of Na, NH.sub.4, and K.
3. The process of claim 1 where the oxygenated solvent is
hexanol.
4. The process of claim 1, where the contacting is performed in a
mixer-settler apparatus.
5. A process for recovering an organic acid, including the steps
of:
providing an aqueous feed containing an organic acid and
impurities, wherein the organic acid is selected from the group
consisting of mono, di, and tricarboxylic acids having from 3-8
carbon atoms;
clarifying the aqueous feed to remove at least a substantial
portion of the impurities therein, producing a clarified feed;
acidulating the clarified liquid feed by adding a quantity of a
mineral acid effective to lower the pH of the feed to between about
1.0 and about 4.5, producing an acidulated feed which is
substantially saturated with respect to at least one electrolyte
selected from the group consisting of MHSO.sub.4, M.sub.2 SO.sub.4,
M.sub.3 PO.sub.4, M.sub.2 HPO.sub.4, MH.sub.2 PO.sub.4, and
MNO.sub.3, where M is selected from the group consisting of Na,
NH.sub.4, and K;
extracting the acidulated feed with an extraction mixture which
consists essentially of (a) water, (b) a mineral acid, in a
quantity effective to maintain the pH of the feed between about 1.0
and about 4.5, and (c) an oxygenated solvent which has limited
miscibility with water and the acidulated feed, the oxygenated
solvent having from 5 to 12 carbon atoms and having at least one
functional group selected from the group consisting of hydroxyl,
ester, keto, ether, carbonyl, and amido, with the extraction
producing a solvent extract and a first raffinate; and
back extracting the solvent extract with an aqueous liquid, thereby
producing an organic acid-rich aqueous extract and an organic
acid-depleted solvent raffinate.
6. The process of claim 5, where the extraction of the acidulated
feed is performed in a mixer-settler apparatus.
7. The process of claim 5, where the back extraction is performed
in a mixer-settler apparatus.
8. The process of claim 5, where the oxygenated solvent has from 6
to 8 carbon atoms.
9. The process of claim 5, where the oxygenated solvent is
hexanol.
10. The process of claim 5, where the ratio of the extraction
mixture to the acidulated feed is between about 3/1 and about 6/1
by weight.
11. The process of claim 5, where the extraction mixture is
substantially saturated with water.
12. The process of claim 5, further including the steps of:
concentrating the organic acid-rich aqueous extract by removing
water; and
decolorizing the extract to remove at least a portion of the
impurities remaining therein.
13. The process of claim 5, further including the steps of:
recovering solvent from the first raffinate by stripping solvent
therefrom; and
recycling the recovered solvent for use in extracting the
acidulated feed.
14. The process of claim 13, further including the steps of:
maintaining the pH of the acidulated feed during the extraction at
a level effective to prevent substantial precipitation of
phosphate, sulfate, nitrate, and chloride salts during the
extraction; and
recovering phosphate, sulfate, nitrate, or chloride salts from the
first raffinate by evaporation after the solvent is stripped
therefrom.
15. The process of claim 5, further including the steps of:
crystallizing a phosphate, sulfate, or nitrate salt from the
acidulated feed;
washing the crystallized salt with an aqueous liquid; and
drying the washed, crystallized salt.
16. The process of claim 5, further including the steps of:
filtering the aqueous feed to remove undesirable impurities;
concentrating the feed by removing a portion of the water therein;
and
decolorizing the feed by contacting it with a decolorizing
agent;
with the filtering, concentrating, and decolorizing of the feed
being done before the feed is acidulated.
17. The process of claim 16, where the decolorizing agent is
selected from the group consisting of granular carbon, powdered
carbon, and decolorizing resin.
18. The process of claim 5, further including the step of:
after extracting the acidulated feed with the extraction mixture of
water, mineral acid, and oxygenated solvent, and before back
extracting the solvent extract with the aqueous liquid, performing
an additional extraction in which an aqueous solution which
contains a quantity of the organic acid is used as the extractant
of the solvent extract from the first extraction step, thereby
producing a second raffinate and a purified solvent extract, with
the latter subsequently being back extracted as specified in claim
5.
19. The process of claim 5, where at least 20% by weight of the
total organic acid values in the aqueous feed are present in the
form of alkali salts of the organic acid, and where the
concentration of organic acid in the feed immediately prior to
acidulation is greater than about 30% by weight.
20. A process for recovering lactic acid, including the steps
of:
providing an aqueous feed containing lactic acid and
impurities;
clarifying the aqueous feed to remove at least a substantial
portion of the impurities therein, producing a clarified feed;
acidulating the clarified feed by adding a quantity of a mineral
acid effective to lower the pH of the feed to between about 1.0 and
about 4.5, producing an acidulated feed which is substantially
saturated with respect to at least one electrolyte selected from
the group consisting of MHSO.sub.4, M.sub.2 SO.sub.4, M.sub.3
PO.sub.4, M.sub.2 HPO.sub.4, MH.sub.2 PO.sub.4, and MNO.sub.3,
where M is selected from the group consisting of Na, NH.sub.4, and
K;
extracting the acidulated feed with an extraction mixture which
consists essentially of (a) water, (b) a mineral acid, in a
quantity effective to maintain the pH of the feed between about 1.0
and about 4.5, and (c) hexanol, with the extraction producing a
hexanol extract and a first raffinate; and
back extracting the hexanol extract with an aqueous liquid, thereby
producing a lactic acid-rich aqueous extract and a lactic
acid-depleted hexanol raffinate.
21. The process of claim 20, where the extraction of the acidulated
feed is performed in a mixer-settler apparatus.
22. The process of claim 20, where the back extraction is performed
in a mixer-settler apparatus.
23. The process of claim 20, where the ratio of the extraction
mixture to the acidulated feed is between about 3/1 and about 6/1
by weight.
24. The process of claim 20, where the extraction mixture is
substantially saturated with water.
25. The process of claim 20, further including the steps of:
concentrating the lactic acid-rich aqueous extract by removing
water; and
decolorizing the extract to remove at least a portion of the
impurities remaining therein.
26. The process of claim 20, further including the steps of:
recovering hexanol from the first raffinate by stripping hexanol
therefrom; and
recycling the recovered hexanol for use in extracting the
acidulated feed.
27. The process of claim 26, further including the steps of:
maintaining the pH of the acidulated feed during the extraction at
a level effective to prevent substantial precipitation of
phosphate, sulfate, and nitrate salts during the extraction;
and
recovering phosphate, sulfate, or nitrate salts from the first
raffinate by evaporation after the solvent is stripped
therefrom.
28. The process of claim 20, further including the steps of:
crystallizing a phosphate, sulfate, or nitrate salt from the
acidulated feed;
washing the crystallized salt with an aqueous liquid; and
drying the washed, crystallized salt.
29. The process of claim 20, further including the steps of:
filtering the aqueous feed to remove undesirable impurities;
concentrating the feed by removing a portion of the water therein;
and
decolorizing the feed by contacting it with a decolorizing
agent;
with the filtering, concentrating, and decolorizing of the feed
being done before the feed is acidulated.
30. The process of claim 29, where the decolorizing agent is
selected from the group consisting of granular carbon, powdered
carbon, and decolorizing resin.
31. The process of claim 20, further including the step of:
after extracting the acidulated feed with the extraction mixture of
water, mineral acid, and hexanol, and before back extracting the
hexanol extract with the aqueous liquid, performing an additional
extraction in which an aqueous solution which contains a quantity
of lactic acid is used as the extractant of the hexanol extract
from the first extraction step, thereby producing a second
raffinate and a purified hexanol extract, with the latter
subsequently being back extracted as specified in claim 20.
32. The process of claim 20, where at least 20% by weight of the
total lactic acid values in the aqueous feed are present in the
form of alkali lactates, and where the concentration of lactic acid
in the feed immediately prior to acidulation is greater than about
30% by weight.
33. A process for recovering lactic acid, including the steps
of:
providing an aqueous feed containing lactic acid and
impurities;
clarifying the aqueous feed to remove at least a substantial
portion of the impurities therein, producing a clarified feed;
concentrating the feed by removing a portion of the water
therein;
decolorizing the feed by contacting it with a decolorizing
agent;
acidulating the clarified feed by adding a quantity of a mineral
acid effective to lower the pH of the feed to between about 1.0 and
about 4.5, producing an acidulated feed which is substantially
saturated with respect to at least one electrolyte selected from
the group consisting of MHSO.sub.4, M.sub.2 SO.sub.4, M.sub.3
PO.sub.4, M.sub.2 HPO.sub.4, MH.sub.2 PO.sub.4, and MNO.sub.3,
where M is selected from the group consisting of Na, NH.sub.4, and
K;
extracting the acidulated feed with an extraction mixture which
consists essentially of (a) water, (b) a mineral acid, in a
quantity effective to maintain the pH of the feed between about 1.0
and about 4.5, and (c) hexanol, with the extraction producing a
first hexanol extract and a first raffinate;
extracting the first hexanol extract with an aqueous lactic acid
solution, thereby producing a second raffinate and a purified
hexanol extract;
back extracting the purified hexanol extract with an aqueous
liquid, thereby producing a lactic acid-rich aqueous extract and a
lactic acid-depleted hexanol raffinate;
recovering hexanol from the first raffinate by stripping hexanol
therefrom;
recycling the recovered hexanol for use in extracting the
acidulated feed;
concentrating the lactic acid-rich aqueous extract by removing
water; and
carbon-treating the concentrated extract to remove at least a
portion of the impurities remaining therein.
Description
FIELD OF THE INVENTION
The present invention relates to a process for recovering organic
acids, such as lactic acid, from fermentation broths by means of
extraction.
BACKGROUND OF THE INVENTION
Lactic acid is an organic acid that has a number of commercial
uses, for example in food manufacturing, pharmaceuticals, plastics,
textiles, and as a starting material in various chemical processes.
Lactic acid is commonly produced by fermentation of sugars, starch,
or cheese whey, using microorganisms such as Lactobacillus
delbrueckii to convert monosaccharides such as glucose, fructose,
or galactose, or disaccharides such as sucrose or lactose, into
lactic acid. The broth that results from the fermentation will
contain unfermented sugars, carbohydrates, amino acids, proteins,
and salts, as well as lactic acid. Some of these materials cause an
undesirable color. The lactic acid must be recovered from the
fermentation broth before it can be put to any substantial use.
A number of processes have been developed in the past to recover
lactic acid or other organic acids from fermentation broths. Some
of these processes involve precipitation of salts followed by
decomposition of the salts, or extraction with certain organic
solvents or water-insoluble amines.
For example, in Baniel U.S. Pat. No 4,275,234, an acid is recovered
from an aqueous solution by extracting the solution with a
water-immiscible organic extractant which comprises at least one
secondary or tertiary amine dissolved in a water-immiscible organic
solvent. The resulting organic extract is separated from the
residual aqueous liquid, and subjected to a stripping operation
with an aqueous liquid for back-extracting at least a substantial
part of the acid from the organic extract into the water, while
leaving substantially all of the amine in the organic phase.
In King U.S. Pat. No. 5,104,492, a carboxylic acid is recovered
from an aqueous solution by contacting the aqueous solution with a
substantially water-immiscible but water-wettable organic solvent.
Two phases are formed, one a carboxylic acid-depleted aqueous
raffinate and the other a carboxylic acid enriched water-wet
solvent extract. The phases are then separated and the carboxylic
acid-enriched water-wet solvent extract is dewatered. This
dewatering decreases the solubility of the acid in the extract
solvent and generates a carboxylic acid-containing bottoms product
from which the acid can be recovered as a precipitate.
However, the recovery processes which have been used in the past
have tended to be relatively expensive, because of having a large
number of steps, poor efficiency of recovery, or for other reasons.
Therefore, a need exists for improved processes for recovery of
lactic acid and other organic acids, which can provide desirable
efficiency of recovery at a reduced cost.
SUMMARY OF THE INVENTION
The present invention relates to a process for the extraction of an
organic acid from an aqueous solution thereof which comprises
contacting such solution with a mixture of (a) water, (b) a mineral
acid in a quantity effective to maintain the pH of the mixture
between about 1.0 and about 4.5, and (c) an oxygenated solvent
which has limited miscibility with water and the acidulated feed,
the oxygenated solvent having from 5 to 12 carbon atoms and having
at least one functional group selected from the group consisting of
hydroxyl, ester, keto, ether, carbonyl, and amido.
In another embodiment, the invention involves a process for
recovering an organic acid which includes providing an aqueous feed
containing an organic acid and impurities, and clarifying the
aqueous feed to remove at least a substantial portion of the
impurities therein, producing a clarified feed. In this context,
"at least a substantial portion" means that at least about 10% by
weight of the impurities that are present are removed. The feed can
optionally be subjected to microfiltration and/or nanofiltration.
The clarified liquid feed is acidulated by adding a quantity of a
mineral acid effective to lower the pH of the feed to between about
1.0 and about 4.5, producing an acidulated feed which is
substantially saturated with respect to at least one electrolyte
selected from the group consisting of MHSO.sub.4, M.sub.2 SO.sub.4,
M.sub.3 PO.sub.4, M.sub.2 HPO.sub.4, MH.sub.2 PO.sub.4, and
MNO.sub.3, where M is selected from the group consisting of Na,
NH.sub.4, and K.
Next, the acidulated feed is extracted with a solvent extraction
mixture which includes (a) water, (b) a mineral acid, in a quantity
effective to maintain the pH of the feed between about 1.0 and
about 4.5, and (c) an oxygenated solvent (such as hexanol) which
has limited miscibility with water and the acidulated feed, the
oxygenated solvent having from 5 to 12 carbon atoms and having at
least one functional group selected from the group consisting of
hydroxyl, ester, keto, ether, carbonyl, and amido, with the
extraction producing a solvent extract and a first raffinate. Then
the solvent extract is back extracted with an aqueous liquid,
thereby producing an organic acid-rich aqueous extract and an
organic acid-depleted solvent raffinate.
The process can further comprise concentrating the organic
acid-rich aqueous extract by removing water and solvent; and
carbon-treating the extract to remove at least a portion of the
impurities remaining therein.
In another embodiment the process can further comprise recovering
solvent from the first raffinate by stripping solvent therefrom;
and recycling the recovered solvent for use in extracting the
acidulated feed. In a variation on this particular embodiment, the
pH of the acidulated feed can be maintained during the extraction
at a level effective to prevent substantial precipitation of
phosphate, sulfate, nitrate, and chloride salts during the
extraction (e.g., pH between about 1.0 and about 4.5, and
preferably between about 1.0 and about 3.5); and phosphate,
sulfate, nitrate, or chloride salts can be recovered from the first
raffinate by evaporation after the solvent is stripped therefrom.
In this context, "level effective to prevent substantial
precipitation" means that no more than de minimis precipitation
will occur.
In another embodiment, an aqueous salt can be recovered by
crystallizing a phosphate, sulfate, or nitrate salt from the
acidulated feed; washing the crystallized salt with an aqueous
liquid, preferably water; and drying the washed, crystallized
salt.
In one preferred embodiment, the aqueous feed is further clarified
prior to acidulation by filtering the aqueous feed to remove
undesirable impurities; concentrating the feed by removing a
portion of the water therein; and decolorizing the feed by
contacting it with a decolorizing agent. The decolorizing agent can
be granular carbon, powdered carbon, or a decolorizing resin.
In another embodiment of the invention, a second solvent extraction
step is added. In particular, after extracting the acidulated feed
with the extraction mixture of water, mineral acid, and oxygenated
solvent, and before back extracting the solvent extract with the
aqueous liquid, an additional extraction is performed in which an
aqueous solution which contains a quantity of the organic acid is
used as the extractant of the solvent extract from the first
extraction step, thereby producing a second raffinate and a
purified solvent extract, with the latter subsequently being back
extracted as specified above. The second raffinate can be recycled
into the acidulated feed.
The quantity of the organic acid in the aqueous extraction of the
oxygenated solvent is preferably adjusted such that there is no net
change in the concentration of the organic acid in the aqueous or
the oxygenated solvent phase at equilibrium.
In a particularly preferred embodiment of the present invention,
the process comprises:
providing an aqueous feed containing lactic acid and
impurities;
clarifying the aqueous feed to remove at least a substantial
portion of the impurities therein, producing a clarified feed;
filtering the clarified feed to remove undesirable impurities;
concentrating the feed by removing a portion of the water
therein;
decolorizing the feed by contacting it with a decolorizing
agent;
acidulating the clarified feed by adding a quantity of a mineral
acid effective to lower the pH of the feed to between about 1.0 and
about 4.5, producing an acidulated feed which is substantially
saturated with respect to at least one electrolyte selected from
the group consisting of MHSO.sub.4, M.sub.2 SO.sub.4, M.sub.3
PO.sub.4, M.sub.2 HPO.sub.4, MH.sub.2 PO.sub.4, and MNO.sub.3,
where M is selected from the group consisting of Na, NH, and K;
extracting the acidulated feed with an extraction mixture which
includes (a) water, (b) a mineral acid, in a quantity effective to
maintain the pH of the feed between about 1.0 and about 4.5, and
(c) hexanol, with the extraction producing a first hexanol extract
and a first raffinate;
extracting the first hexanol extract with an aqueous lactic acid
solution, thereby producing a second raffinate and a purified
hexanol extract;
back extracting the purified hexanol extract with an aqueous
liquid, thereby producing a lactic acid-rich aqueous extract and a
lactic acid-depleted hexanol raffinate;
recovering hexanol from the first raffinate by stripping hexanol
therefrom;
recycling the recovered hexanol for use in extracting the
acidulated feed;
concentrating the lactic acid-rich aqueous extract by removing
water; and
carbon-treating the concentrated extract to remove at least a
portion of the impurities remaining therein.
Additionally, a portion of the lactic acid-rich aqueous extract may
be recycled to be used as the aqueous lactic acid solution to
extract the first hexanol extract.
The organic acids which may be recovered by the process of the
present invention include mono-, di-, and tricarboxylic acids
comprised of 3-8 carbon atoms. Examples include, but are not
limited to, lactic acid, citric acid, malic acid, maleic acid,
fumaric acid, adipic acid, succinic acid, tartaric acid,
.alpha.-ketoglutaric acid, and oxaloacetic acid.
One advantage of the present invention relates to performing the
extraction at saturation, or substantially saturated conditions
(e.g., .gtoreq.90% of saturation) with the appropriate salt of the
mineral acid used for the acidulation. The higher the salt
concentration, the higher is the driving force for extraction of
the lactic acid into the hexanol phase.
Other advantages include the use of various recycle streams which
tend to minimize the number of effluent streams. Further, working
at higher concentrations of lactic acid reduces the volumes of and
number of extraction stages. Thus, the present invention has
advantages of simplicity, reduced cost, and reduced effluent
compared to the prior art.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a process flow diagram for a particular embodiment of the
present invention.
FIG. 2 is a plan view of a mixer-settler apparatus that can be used
in the process of the present invention.
FIG. 3 is a side cross sectional view of the mixer-settler of FIG.
2, taken along axis X--X.
FIG. 4 is a graph of the percent of lactate and phosphate that are
in salt form at different pH values, and of the difference between
the percentages for the two materials.
FIG. 5 is a graph of the relationship between pH and the
concentration of various components in the soluble phase.
FIG. 6 is a graph of the relationship between pH and quantity of
precipitate, supernatant, and total precipitate plus supernatant
per mole of lactic acid.
FIG. 7 is a graph of the relationship between pH and the
distribution of soluble and insoluble phases.
FIG. 8 is a graph of the relationship between pH and the moles of
various components per mole of lactic acid.
FIG. 9 is a graph of the relationship between pH and the moles of
various components per kg of solution.
FIG. 10 is a graph of the relationship between pH and the grams of
various components per kg of solution.
FIG. 11 is a graph of the relationship between pH and the ratio of
moles of phosphoric acid to moles of lactic acid.
FIG. 12 is a graph of the amount of precipitate at different pH's
for a broth sample acidulated with H.sub.2 SO.sub.4.
FIG. 13 is a graph of the moles of H.sub.2 SO.sub.4 added and
precipitate formed for different samples of acidulated broth.
FIG. 14 is a graph of the percentage recovery in the solvent phase
of various components at varying levels of broth saturation.
FIG. 15 is a graph of the percent lactic acid removed in
extractions employing different acids.
FIG. 16 is a graph of the percent lactic acid removed in a
cross-current back extraction.
FIG. 17 is a graph of the change in lactic acid content of the feed
vs. that of the aqueous phase for back extractions.
FIG. 18 is a graph showing calculated numbers of back extraction
stages required to reach a given level of lactic acid recovery.
FIG. 19 is a graph showing the percent lactic acid recovery after
each of several cross-current back extractions.
DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS
The term lactic acid is used in this patent to include either
optical isomer of lactic acid, as well as racemic mixtures of those
optical isomers. Further, it includes mixtures of lactic acid
monomers, dimers, trimers, and other lactic acid polymers of low
molecular weight (generally below about 740 m.w.; e.g. a polymer of
about DP 10).
FIG. 1 shows a particular embodiment of a process in accordance
with the present invention. Lactic acid can initially be prepared
by fermentation as is known in the art. An aqueous solution
containing lactic acid, in particular a fermentation broth 10, is
the result of that process, and the feed for the present
process.
Although the specific process embodiment of the invention described
in this patent recovers lactic acid from a fermentation broth, the
present invention is not limited to recovering the products of
fermentation. The process of the present invention can be used in
any situation where an organic acid is to be recovered from an
aqueous solution or dispersion. For example, the process can be
used to recover lactic acid from aqueous solutions of lactic
acid-containing biopolymers, after performing the necessary process
steps to free the lactic acid from the biopolymer.
The broth 10 will typically contain less than 25% by weight lactic
acid. Preferably at least 80% by weight of the total lactate values
in the broth are present as Na, K, or NH.sub.4 lactates.
The fermentation broth 10 is clarified 12 by microfiltration or
other procedures such as centrifugation, filter pressing, or rotary
vacuum filtration, producing a particulate-free, filtered,
fermentation broth 14. The biomass 16 removed by filtration can be
recycled to the fermentation bioreactor, or can be dried and used,
for example, as animal feed. The filtered broth 14 is further
purified by ultrafiltration and/or nanofiltration 18 to further
reduce the amount of undesirable organic impurities in the
broth.
An example of a filtration process that can be used is as follows:
Feedstock was prepared by microfiltration of fermentation broth
followed by nanofiltration of the microfiltered permeate. A 0.02
micron Membralox ceramic element from U.S. Filter was used for the
microfiltration. A multi-leaf spiral wound polymeric element with a
180 MW cutoff from Desalination Systems, Inc. was used for the
nanofiltration process. This clean-up procedure yielded a feedstock
with about 95-99% of the material having a molecular weight less
than or equal to ammonium lactate.
The broth is then concentrated by standard evaporative techniques
to a solids concentration of between 50% to 85% with a lactate
content of between 38% to 65% respectively. The broth is then
decolorized 20, by contacting the broth with granular or powdered
carbon, or a decolorizing resin. Suitable commercial products for
this purpose include:
powdered carbon: Nuchar-SA, Westraco, Darco S51, ICI Chem.;
granular carbon: Calgon CPG, Americon Norit; and
decolorizing resin: Dowex Optipore Adsorbent.
The broth may also be further concentrated 22, either after or
before the decolorization step 20. The lactic acid concentration in
the resulting solution is typically in the range of from about 30%
to about 90% by weight.
The decolorized, concentrated broth is then acidulated 24 with an
acid, such as H.sub.3 PO.sub.4, H.sub.2 SO.sub.4, HCl, or
HNO.sub.3, to a pH between about 1.0 and about 4.5. (Tests of
acidulated broth having pH ranging from 4.3 to 3.5 showed the
greatest precipitation at pH 3.5, although pH of 3.5-3.9 yielded
the highest percentage of lactic acid extracted in the solvent.) At
this point, the acidulated broth contains at least 35% lactic acid
by weight and is substantially saturated with respect to at least
one of the electrolytes MHSO.sub.4, M.sub.2 SO.sub.4, M.sub.3
PO.sub.4, M.sub.2 HPO.sub.4, MH.sub.2 PO.sub.4, and MNO.sub.3,
where M is selected from the group consisting of Na, NH.sub.4, and
K.
After acidulation 24, phosphate, sulfate, and/or nitrate salts are
crystallized 26, and then the salts are separated 28 from the
acidulated broth by techniques typical in the industry for
separation of an inorganic salt from its corresponding broth, such
as solid bowl centrifugation, basket centrifugation, filtration,
vacuum filtration, and the like, producing a wet crystal cake 30.
The wet crystal cake 30 is then washed 32 with water 34, and dried
36 by technique typical in the industry for drying an inorganic
salt, producing a dried salt 38, for example ammonium phosphate.
The water used in the washing step 32 is recycled 40 back to the
concentrated broth prior to acidulation 24, and can suitably be
mixed with the mineral acid 42 (e.g., phosphoric acid).
The clarified, acidulated broth 50 is then subjected to a first
extraction 52 with a solvent extraction mixture 54 which includes,
and preferably consists essentially of, (a) water, (b) a mineral
acid, and (c) an oxygenated organic solvent. The oxygenated solvent
has limited miscibility with water and the acid broth, preferably
has between about 5 and about 12 carbon atoms, and carries at least
one functional group selected from the group consisting of
hydroxyl, ester, keto, ether, carbonyl, and amido. The oxygenated
solvent more preferably has 6-8 carbon atoms. An especially
preferred solvent is hexanol. The ratio of the solvent mixture 54
to the acidulated broth 50 is preferably between about 3/1 and
about 6/1 by weight, preferably about 4/1.
Limiting condition extractions with the solvents hexanol, butanol,
butyl acetate, isopropyl ether, 3-methyl-1-butanol, dodecanol,
octanol, hexanes, and heptanol gave the following findings: butanol
did not phase separate, 3-methyl-1-butanol required an equal weight
addition of solvent to do so, and hexanol removed the largest
quantity of lactic acid under limiting conditions.
As an example of the limited miscibility of the oxygenate organic
solvent with water, Lactic Acid, Properties and Chemistry of Lactic
Acid and Derivatives, by C. H. Holten, Verlag Chimie (1971), at
pages 43 and 45 (which is incorporated here by reference),
indicates that at 25.degree. C. the solubility of water in
1-hexanol is 7.9% and the solubility of hexanol in water is
0.5%.
The use of acid in the oxygenated organic solvent keeps the pH in a
range where the lactic acid is primarily in acid form rather than
salt form. As the pH goes up, a greater percentage of the lactic
acid converts to the salt form, which is much less soluble in
hexanol. It is preferred to keep the amount of lactic acid in the
salt form at less than 30%, which indicates that the pH should
preferably be kept below 3.5.
If phosphoric acid is used in the solvent extraction mixture, there
is a tendency for increased salt formation and thus an increased
chance of precipitation. Using a different acid such as
hydrochloric acid can reduce the chance of precipitation, because
ammonium chloride is formed rather than ammonium dihydrogen
phosphate, the latter already being at a saturation level. However,
the use of an additional acid is not entirely desirable, and it may
be preferably to use other methods of reducing or eliminating
precipitation.
The amount of water in the mixture 54 is preferably that of
substantial saturation (i.e., at least 90% saturated), and is most
preferably that of saturation. A portion of this stream will come
from a back extraction step 68 and will thus carry water at a
saturation level. The addition of the phosphoric acid 94 will also
carry some water with it since the phosphoric acid in preferably at
75% concentration, but the addition of the phosphate will allow an
increase in the quantity of water that the hexanol will hold. The
acid is added in an amount effective to maintain the pH of the
broth between about 1.0 and about 4.5 during the first extraction
52, in order to optimize the extraction efficiency.
Examples of suitable compositions for the process of the present
invention are as follows:
acidulated broth at pH 3.0
53.14% lactic
3.52% PO.sub.4
2.55% NH.sub.3
28.83% water
hexanol extractant
6.0% water
0.7% H.sub.3 PO.sub.4
93.3% hexanol
aqueous phase at equilibrium
27.67% lactic acid
47.09% water
0.25% hexanol
7.71% PO.sub.4
3.56% NH.sub.3
13.72% other
organic phase at equilibrium
8.04% lactic acid
0.03% PO.sub.4
0.08% NH.sub.3
5.81% water
86.26% hexanol
equilibrium ratio=6.23/1 (solvent/aqueous)
The resulting first raffinate 56 is sent to a solvent recovery
system, which will be discussed further below.
The first solvent extract 58 is then subjected to a second
extraction 60 in order to purify the extract. An aqueous solution
62 is used which consists essentially of water and a limited
quantity of pure lactic acid, preferably no more than about 25%
lactic acid by weight. The ratio of the first solvent extract 58 to
the aqueous lactic acid solution 62 is preferably between about 4/1
and about 20/1 by weight. This second extraction produces a second
raffinate 64 which is recycled by combining it with the acidulated
broth 50 for use in the first extraction 52. A purified, second
solvent extract 66 is also produced, containing primarily solvent,
lactic acid, and water.
The purified solvent extract 66 is then back extracted 68 with an
aqueous liquid, preferably water 70, producing a lactic
acid-depleted solvent raffinate 72 and a lactic acid-rich aqueous
extract 74. The ratio of the purified solvent extract 65 to the
water 70 is preferably between about 4/1 and about 10/1 by weight.
A portion of the lactic acid-rich aqueous extract 74 is recycled 76
to the aqueous lactic acid solution 62 for use in the second
extraction 60. The remainder of the lactic acid-rich aqueous
extract 74 is concentrated 76, thus removing a condensate 84 which
is sent to a solvent recovery system. Minor contaminants are then
removed by a decolorizing treatment 78 with carbon or a
decolorizing resin. After this treatment, used carbon 80 is
recycled to the earlier decolorization step 20.
The final lactic acid solution 82 will typically have a
concentration of between about 30%-90% by weight.
The lactic acid-depleted solvent raffinate 72 is recycled back to
the first extraction 52, where it is combined with the necessary
additional ingredients to make up the solvent extraction mixture
54. The first raffinate 56 and the condensate 84 are sent to a
solvent stripper 86, which separates solvent 88 from aqueous waste
90. The aqueous waste 90, which will usually contain ammonium
dihydrogen phosphate, other salts, proteinaceous materials, and
carbohydrates, can be used as animal feed or fertilizer. The
recovered solvent 88 is sent to a solvent purification unit 92. The
solvent purification unit will preferably consist of a standard
construction for the heterogeneous distillation of azeotropic
liquids. Some or all of the lactic acid-depleted solvent raffinate
72 is also passed through the solvent purification unit 92. The
desired amount of mineral acid 94 is added to the solvent recycle
stream 96, together with a controlled amount of water 98 to
complete the desired makeup of the solvent extraction mixture 54
for the first extraction 52.
The extraction steps can be carried out in batch operation or
continuously, and may be conducted by any conventional liquid phase
extraction method, including for example counter-current
liquid-liquid extraction methods or extraction columns which are
known to persons skilled in this field. Centrifugation can also be
used. Additional extraction stages and/or steps can be used if
desired.
In a particular embodiment of the present invention, the extraction
steps are carried out in a multi-stage mixer-settler apparatus,
such as the Robatel Model UX 1.1 mixer-settler (Robatel Inc.,
Pittsfield, Mass.). In this type of extraction apparatus, each
stage includes at least a mixer and a settler. The mixer brings the
solvent and the feed into intimate contact with each other. In the
settler portion of each stage, a lighter phase rises to the top of
the settler and overflows a weir to an adjacent stage in one
direction. A heavier phase sinks to the bottom of the settler, and
underflows a separate weir into a different adjacent stage in a
different direction.
FIGS. 2 and 3 show one embodiment of a mixer-settler 100,
containing eight stages 102a-102h. Each stage has a mixer 104
driven by a motor 106 and having a shaft 108 and a turbine 110.
Solvent 112 can be fed in one end of the apparatus, while the feed
114 is fed into the other end. In each stage 102, the mixer 104
mixes the solvent and feed, and they then separate at least to some
degree into phases. A lighter phase will overflow an overflow weir
116 into an adjacent chamber, while a heavier phase will underflow
an underflow weir 118 into a separate chamber that is also
adjacent. The ultimate result is an extract 120 and a raffinate
122.
In an alternate embodiment of the process, instead of crystallizing
and separating the salt (e.g., ammonium dihydrogen phosphate)
before extraction, the acidulated broth fed into the extraction
would contain both lactic acid (in hydrogen form) and the phosphate
salt. The extraction would be operated so as to be borderline
saturated with ammonium dihydrogen phosphate, using pH in the same
range as stated above, thereby preventing any substantial
precipitation of the salt during extraction. The ammonium phosphate
would be recovered from the raffinate stream 56 by stripping of the
hexanol, followed by evaporation, leaving the salt.
EXAMPLE 1
Calculations were performed to evaluate the pH distributions of
salt and acid forms of lactic acid and phosphoric acid, using the
Henderson-Hasselbach equation (pH=pK.sub.a +log salt/acid), and the
following values:
lactic acid pK=3.858
H.sub.3 PO.sub.4 pK.sub.1 =2.15
The results are plotted in FIG. 4. (Note that the above equation is
generally used for dilute aqueous solutions; the relationship may
be slightly different in the system used here.) At pH 4.1, about
64% of lactic acid values will exist as ammonium lactate, with the
remaining about 36% as acid. The difference between the lactate and
phosphate curves will theoretically be the largest at a pH of about
3.0, and thus that pH may be preferable for the extraction.
EXAMPLE 2
A clarified fermentation broth was obtained, shown in Table 1 as
sample 310. A quantity of broth (C) was acidulated with a quantity
of 75% phosphoric acid (D) and the resulting pH was measured (B).
The supernatant was removed after centrifugation and analyzed as
shown (F, G, H, I). The only assumption made was that all of the
lactic acid was in the soluble phase.
TABLE 1A
__________________________________________________________________________
C D E F H I J A B g g 75% Total Wt % NH3 G % Lactic % PO4 g H3PO4
Sample No pH Sample H3PO4 C + D Sol % H2O Sol Sol Sol D*0.75
__________________________________________________________________________
310 6.079 10.00 0 10.00 10.84 16.5 62.89 0.17 0.0000 311 5.204
10.00 1.40 11.40 9.16 19.2 58.87 2.41 1.0500 312 4.603 10.01 2.93
12.94 7.71 22.6 59.49 1.96 2.1975 313 4.204 10.02 3.98 14.00 5.95
24.7 57.93 2.04 2.9850 314 3.689 10.04 5.31 15.35 4.23 27.3 57.40
2.46 3.9825 315 3.134 10.03 6.64 16.67 2.79 29.5 55.44 3.28 4.9800
316 2.389 10.00 7.92 17.92 1.72 31.2 52.36 5.89 5.9400 317 1.600
10.08 9.33 19.41 1.43 30.8 44.86 11.14 6.9975 318 0.965 10.00 10.59
20.59 1.70 29.4 41.19 19.39 7.9425 319 0.699 10.01 11.91 21.92 1.95
28.3 35.99 26.24 8.9325
__________________________________________________________________________
TABLE 1B
__________________________________________________________________________
L N O P K % Lactic All M g Ppt Moles Moles Q A B g Lactic Sol g
Soln Calc Calc Lactic H3PO4 M H3PO4/M Lactic Sample No pH C* 0.6289
K* 100/E K/H * 100 E - M K/90.08 J/98.0 P/O
__________________________________________________________________________
310 6.079 6.2890 62.89 0.0698 0.0000 311 5.204 6.2890 55.17 10.683
0.717 0.0698 0.0107 0.1535 312 4.603 6.2953 48.65 10.582 2.358
0.0699 0.0224 0.3209 313 4.204 6.3016 45.01 10.878 3.122 0.0700
0.0305 0.4354 314 3.689 6.3142 41.13 11.000 4.350 0.0701 0.0406
0.5798 315 3.134 6.3079 37.84 11.378 5.292 0.0700 0.0508 0.7257 316
2.389 6.2890 35.09 12.011 5.909 0.0698 0.0606 0.8682 317 1.600
6.3393 32.66 14.131 5.279 0.0704 0.0714 1.0146 318 0.965 6.2890
30.54 15.268 5.322 0.0698 0.0810 1.1609 319 0.699 6.2953 28.72
17.492 4.428 0.0699 0.0911 1.3042
__________________________________________________________________________
TABLE 1C
__________________________________________________________________________
R U V W Moles S T Moles PO4 Salt Moles A B NH4H2PO4 Ppt Moles NH3
Sol Moles PO4 Sol ppt (PO4)/Acid NH4H2PO4 Sol Sample No pH N/115.03
F*.01*M/17.03 I*.01*M/94.97 P - T 10 (B -2.15) (V*T)(1 + V)
__________________________________________________________________________
310 6.079 311 5.204 0.0062 0.0575 0.0027 0.0080 1132.400 0.0027 312
4.603 0.0205 0.0479 0.0022 0.0202 283.792 0.0022 313 4.204 0.0271
0.0380 0.0023 0.0281 113.240 0.0023 314 3.689 0.0378 0.0273 0.0028
0.0378 34.594 0.0028 315 3.134 0.0460 0.0186 0.0039 0.0469 9.638
0.0036 316 2.389 0.0514 0.0121 0.0074 0.0532 1.734 0.0047 317 1.600
0.0459 0.0119 0.0166 0.0548 0.282 0.0036 318 0.965 0.0463 0.0152
0.0312 0.0499 0.065 0.0019 319 0.699 0.0385 0.0200 0.0483 0.0428
0.035 0.0017
__________________________________________________________________________
TABLE 1D
__________________________________________________________________________
X Y Z AA AB Moles g Solution/ g Ppt/Mole Total g/Mole % AC A B
H3PO4 Sol Mole Lactic Lactic Lactic Precipitate % Soluble Sample No
pH T - W M/O N/O Y + Z 100*Z/AA 100*Y/AA
__________________________________________________________________________
310 6.079 311 5.204 0.0000 153.02 10.27 163.29 6.29 93.71 312 4.603
0.0000 151.42 33.74 185.16 18.22 81.78 313 4.204 0.0000 155.50
44.63 200.13 22.30 77.70 314 3.689 0.0001 156.93 62.05 218.99 28.34
71.66 315 3.134 0.0004 162.48 75.58 238.06 31.75 68.25 316 2.389
0.0027 172.04 84.64 256.68 32.97 67.03 317 1.600 0.0129 200.80
75.01 275.81 27.20 72.80 318 0.965 0.0293 218.69 76.23 294.92 25.85
74.15 319 0.699 0.0467 250.29 63.36 313.66 20.20 79.80
__________________________________________________________________________
TABLE 1E
__________________________________________________________________________
AD AE AF AG AH % Mol AmPhos Mol AmPhos Mol H3PO4 Mole AmPhos Ppt/ A
B Precipitate PPT/Mol Lactic Sol/Mol Lactic Sol/Mol Lactic Kg Soln
Sample No pH 100 - AC U/V W/O X/O AE *1000/Y
__________________________________________________________________________
310 6.079 311 5.204 6.29 0.1146 0.0388 0.0000 0.749 312 4.603 18.22
0.2896 0.0311 0.0001 1.913 313 4.204 22.30 0.4020 0.0331 0.0003
2.585 314 3.689 28.34 0.5391 0.0395 0.0011 3.435 315 3.134 31.75
0.6696 0.0508 0.0053 4.121 316 2.389 32.97 0.7615 0.0677 0.0390
4.426 317 1.600 27.20 0.7791 0.0518 0.1838 3.880 318 0.965 25.85
0.7143 0.0274 0.4191 3.266 319 0.699 20.20 0.6127 0.0236 0.6679
2.448
__________________________________________________________________________
TABLE 1F
__________________________________________________________________________
AI AJ AK Al AM AN Mole AmPhos Mole H3PO4 Mole Lactic/ g Am Phos g
H3PO4 g Lactic A B Sol/Kg Soln Kg Soln Kg Soln Sol/Kg Soln Sol/Kg
Soln Sol/Kg Soln Sample No pH AF*1000/Y AG*1000/Y 1*1000/Y
AI*115.03 AJ*98.0 AK*90.08
__________________________________________________________________________
310 6.079 311 5.204 0.254 0.000 6.535 29.16 0.02 588.70 312 4.603
0.206 0.001 6.604 23.66 0.07 594.90 313 4.204 0.213 0.002 6.431
24.49 0.18 579.30 314 3.689 0.252 0.007 6.372 28.96 0.71 574 00 315
3.134 0.313 0.032 6.155 35.99 3.18 554.40 316 2.389 0.393 0.227
5.813 45.25 22.23 523.60 317 1.600 0.258 0.915 4.980 29.67 89.68
448.60 318 0.965 0.125 1.917 4.573 14.40 187.82 411.90 319 0.699
0.094 2.669 3.995 10.87 261.51 359.90
__________________________________________________________________________
FIGS. 5-11 summarize the results of this experiment
graphically.
EXAMPLE 3
Concentrated fermentation broth (containing 78.24% lactic acid,
3.18% water, 12.28% NH.sub.3, 1472 ppm PO.sub.4, and 5115 ppm Cl)
was diluted with water such that the resulting lactic acid
concentration was 65.41%. The pH of this diluted broth was 5.41.
Portions of the broth were acidified with sulfuric acid (96.1%)
such that a series of samples were produced in a pH range of 5 to
0.3. The samples were centrifuged and the supernatant was removed
and analyzed for lactic acid. The only assumption made was that all
of the lactic acid was in the soluble phase. See Table 2 below and
FIGS. 12 and 13 for the results.
TABLE 2
__________________________________________________________________________
g H2SO4 moles moles added moles g g wet g ammonium cum g broth g
lactic lactic (96.1%) g H2SO4 H2SO4 supernate ppt pH g ppt soluble
sulfate moles
__________________________________________________________________________
20.04 13.026 0.1446 1 0.962 0.0098 16.68 4.36 4.96 1.35 19.69 0.010
0.01 20.02 13.013 0.1445 2.03 1.95 0.0199 15.25 6.8 4.51 2.32 19.73
0.018 0.028 20.03 13.0195 0.1445 3.02 2.91 0.0296 14.46 8.59 4.06
3.71 19.34 0.028 0.056 20.01 13.0065 0.1444 4.04 3.89 0.0396 14.02
10.03 3.51 4.18 19.87 0.032 0.087 20 13 0.1443 4.5 4.33 0.0441
14.65 9.85 3.23 5.05 19.45 0.038 0.126 20.01 13.0065 0.1444 5.03
4.84 0.0493 14.98 10.06 2.9 5.78 19.26 0.044 0.169 20 13 0.1443 5.5
5.29 0.0539 15.44 10.06 2.53 5.14 20.36 0.039 0.208 20.02 13.013
0.1445 6.05 5.82 0.0593 16.56 9.51 1.94 4.82 21.25 0.036 0.245
20.03 13.0195 0.1445 6.64 6.39 0.0651 17.39 9.28 0.73 3.46 23.21
0.026 0.271 20.03 13.0195 0.1445 7.08 6.81 0.0694 17.78 9.33 0.56
2.29 24.82 0.017 0.288 20 13 0.1443 7.56 7.27 0.0742 16.81 10.75
0.36 2.35 25.21 0.018 0.306 20.04 13.026 0.1446 8.04 7.73 0.0789
15.11 12.97 0.3 0.5 27.58 0.004 0.310
__________________________________________________________________________
EXAMPLE 4
A concentrated feed broth was acidulated with one molar equivalent
of 75% H.sub.3 PO.sub.4. Water was added to dissolve salts. The pH
was 2.12 and after dilution the broth contained 16.80% lactic acid.
1.13 g of hexanol was added to 81.22 g of this feed, resulting in
cloudiness. The mixture was allowed to sit; no cloudiness was
observed. 5.23% lactic acid was recovered from the aqueous phase.
Later ca. 0.18 g of precipitate was noted in the extracted
feed.
EXAMPLE 5
Several acidulated broths containing lactic acid were extracted in
a cross-current process. A clarified, filtered, acidulated broth
containing lactic acid designated sample 5A was extracted six
times. The acidulated broth feed contained 55.03% lactic acid by
weight, 3.26% PO.sub.4, 4.33% NH.sub.3, 30.21% water, and had a pH
of 4.1. The extractant contained 100 g hexanol (95.06% by weight of
the total extractant), 0.2 g of 85% H.sub.3 PO.sub.4 (0.19% by
weight), and 5.0 g water (4.78% by weight). This amount of water
represented approximate saturation of the extractant mixture. Seven
g of initial acidulated broth feed were extracted with 35 g of
extractant (i.e., a 5/1 solvent/feed ratio by weight).
TABLE 3 ______________________________________ Sample 5A Ex- %
Lactic traction Feed Extractant Acid in pass (g) (g) Extract (g)
Extract Comments ______________________________________ 1 7.03
35.13 35.56 5.01 2 5.34 35.07 35.12 1.36 precipitate forming 3 5.06
35.08 34.95 0.72 more precipitate 4 5.01 35.03 34.89 0.46 5 4.94
35.07 34.69 0.31 6 4.95 35.16 35.30 0.39
______________________________________
The pH of the remaining aqueous phase after the sixth extraction
was 5.3. The aqueous phase weighed 4.59 g and contained 12.87%
lactic acid. Thus 75.5% of the lactic acid in the original feed was
extracted.
It appeared that the amount of acid in the extractant was not
enough to keep the pH stable during extraction, or, alternatively,
that the starting pH of the acidulated broth preferably should have
been lower.
Another acidulated broth containing lactic acid (designated sample
5B) was extracted. The broth prior to acidulation contained 66.09 g
lactic acid (0.7337 moles) out of a total weight of 101.73 g. It
was acidulated with 68.30 g of 75% H.sub.3 PO.sub.4 (0.5227 moles),
creating a pH of 3.0 and a temperature rise from 25.degree. C. to
55.degree. C.
The resulting NH.sub.4 H.sub.2 PO.sub.4 was removed by
centrifugation and decantation. The sediment mixture totalled
113.82 g. The amount of NH.sub.4 H.sub.2 PO.sub.4 formed was
calculated by using the dilution of lactic acid concept to be 48.5
g (0.422 moles). The clarified broth remaining after the salt was
removed totaled 56.21 g, and was made up of 33.06% (weight) lactic
acid, 3.73% PO.sub.4, 2.67% NH.sub.3, and 28.64% water.
The extractant was made up of 100 g hexanol (94.79% by weight of
the total extractant), 0.5 g of 75% H.sub.3 PO.sub.4 (0.36% by
weight), and 5.0 g water (5.09% by weight). The acidulated,
clarified broth was extracted six times, using 32.0 g of the
extractant per cycle, in a 4/1 solvent/feed ratio by weight.
TABLE 4 ______________________________________ Sample 5B Ex- %
Lactic traction Feed Extractant Acid in pass (g) (g) Extract (g)
Extract Comments ______________________________________ 1 8.08
32.05 34.85 8.17 2 5.15 32.02 32.44 2.12 3 4.52 32.05 32.17 0.92
precipitate start 4 4.18 32.08 31.80 0.60 5 4.25 32.14 32.17 0.44 6
4.12 32.02 32.02 0.33 ______________________________________
About 4.27 g of lactic acid was extracted out of a total of about
4.39 in the feed. Thus 97.27% of the lactic acid in the original
feed was extracted.
A large amount of precipitate formed during the extraction. Also,
quite a bit of liquor remained with the precipitate after
separation by centrifugation. This latter problem might have been
minimized if filtration had been used instead of
centrifugation.
Five other extractions were performed. The extraction parameters
and results are shown in Table 5 below.
TABLE 5
__________________________________________________________________________
Cross-Current Extraction Cumulative % Lactic Acid Collected in
Solvent Extraction Sample No. Number 5A 5B 5C 5D 5E 5F 5G
__________________________________________________________________________
1 45.99 64.92 40.00 62.50 73.64 67.12 88.60 2 58.39 80.64 49.45
74.55 86.49 84.67 99.48 3 64.85 87.47 60.36 78.12 89.32 90.52
100.00 4 68.98 91.80 68.36 79.68 90.41 95.63 100.00 5 71.82 94.99
72.00 80.57 91.28 97.87 100.00 6 75.44 97.50 N/A 81.24 91.72 98.35
100.00 Conditions pH 4.10 3.00 4.10 2.91 2.65 3.00 1.31 Solvent:
5:1 4:1 3.4:1 4:1 4:1 4:1 4:1 feed ratio Solvent (Hexanol) Content
H3PO4 0.16% 0.36% -- -- -- 0.79% -- H2O 4.78% 4.86% -- saturated
saturated 6.00% saturated
__________________________________________________________________________
EXAMPLE 6
Phosphoric acid, acidulated fermentation broth (comprising 53.14%
lactic acid, 3.52% PO.sub.4, 2.55% NH.sub.3, and 28.83% water, pH
3.0) was used "as is" or diluted with water to produce a series of
solutions containing ammonium dihydrogen phosphate at 100%, 98%,
95%, 93%, 90%, and 80% of saturation. A 4:1 solvent/aqueous ratio
was used. The solvent/extractant was 92.79% hexanol, 6.51% water,
and 0.7% phosphoric acid. Precipitate formed in the first stage for
all but the 90% and 80% samples. The percentage lactic acid
recovery decreased only slightly, from 65.13% at full saturation to
62.09% recovery in the 80% saturated sample.
TABLE 6
__________________________________________________________________________
g broth g g dil Satur. used water Theoret. % Theor. % Theor. %
Theoret. % broth used Sample Level for dilut. added Lactic Lactic
PO4 PO4 NH3 NH3 Water Water for extra
__________________________________________________________________________
c. 6A 100% 10 0 55.39% 53.14% 3.27% 3.52% 2.56% 2.55% 28.70% 28.83%
8.01 6B 98% 10 0.21 54.28% 53.18% 3.20% 3.56% 2.51% 2.49% 30.17%
30.24% 8.02 6C 95% 10 0.51 52.62% 51.32% 3.11% 3.40% 2.43% 2.48%
32.16% 32.28% 7.99 6D 93% 10 0.75 51.51% 51.11% 3.04% 3.37% 2.38%
2.33% 33.67% 33.73% 8.03 6E 90% 10 1.12 49.85% 48.76% 2.94% 2.90%
2.30% 2.32% 35.88% 36.27% 8.02 6F 80% 10 2.52 44.31% 43.30% 2.62%
3.15% 2.05% 1.97% 43.05% 43.14% 8.03
__________________________________________________________________________
g g g Solvent Phase lactic g PO4 g NH3 water solvent g solvent g
lactic % lactic Sample in in in in used out % lactic out recovery
PO4 ppm % PO4 g PO4
__________________________________________________________________________
6A 4.257 0.282 0.204 2.309 32 34.48 8.04% 2.772 65.13% 279 0.0279%
0.0096 6B 4.265 0.286 0.200 2.425 32.03 34.33 8.05% 2.764 64.80%
252 0.0252% 0.0087 6C 4.100 0.272 0.198 2.579 32.05 34.28 7.57%
2.595 63.29% 261 0.0261% 0.0089 6D 4.104 0.271 0.187 2.709 32.04
34.35 7.57% 2.600 63.36% 254 0.0254% 0.0087 6E 3.911 0.233 0.186
2.909 32.01 34.15 7.03% 2.401 61.39% 196 0.0196% 0.0067 6F 3.477
0.253 0.158 3.464 32.02 34 6.35% 2.159 62.09% 198 0.0198% 0.0067
__________________________________________________________________________
Solvent Phase g water % NH3 picked up % change Sample % PO4 recov.
% NH3 g NH3 recovery % water g water in* g water out from aqueous
in water
__________________________________________________________________________
6A 3.41% 0.076% 0.0262 12.83% 5.81% 1.92 2.0033 0.0833 4.16% 6B
3.03% 0.066% 0.0227 11.35% 5.52% 1.9218 1.8950 -0.0268 -1.41% 6C
3.29% 0.056% 0.0192 9.69% 5.91% 1.923 2.0259 0.1029 5.08% 6D 3.22%
0.050% 0.0172 9.18% 6.02% 1.9224 2.0679 0.1455 7.03% 6E 2.88%
0.037% 0.0126 6.79% 6.08% 1.9206 2.0763 0.1557 7.50% 6F 2.66%
0.032% 0.0109 6.88% 6.35% 1.9212 2.1590 0.2378 11.01%
__________________________________________________________________________
See FIG. 14.
EXAMPLE 7
Three cross-current extractions runs with a lactic acid solution
were done with hexanol, 6% water, and the following acids: 0.7%
phosphoric, 0.26% hydrochloric, and 0.46% sulfuric. The ratio of
solvent to aqueous phases was 4:1.
TABLE 7
__________________________________________________________________________
Hexanol Extraction with Different Acids g Solvent % Lactic Acid g
lactic % lactic Phase % Lactic g Lactic Cum g Removed pH g
raffinate % lactic remaining remaining
__________________________________________________________________________
0.7% H.sub.3 PO.sub.4 ; Extraction 1 35.13 8.72 3.06 3.06 67.11% --
2 32.42 2.47 0.80 3.86 84.65% -- 3 31.84 0.84 0.27 4.13 90.57% 4.32
4 31.92 0.73 0.23 4.36 95.61% 4.04 5 31.73 0.32 0.10 4.46 97.81%
3.55 6 31.64 0.07 0.02 4.48 98.25% 3 5.03 0.14% 0.007 0.05% 0.26%
HCl; Extraction 1 34.95 8.8 3.08 3.08 67.54% -- 2 32.63 2.34 0.76
3.84 84.19% -- 3 32.02 0.25 0.08 3.92 85.95% 4.08 4 31.99 0.13 0.04
3.96 86.94% 4.06 5 31.90 0.44 0.14 4.10 89.92% 3.55 6 31.81 0.08
0.03 4.13 90.57% 2.32 4.36 0.78% 0.034 0.24% 0.46% H.sub.2 SO.sub.4
1 35.09 8.91 3.13 3.13 68.64% 4.09 2 32.4 2.61 0.85 3.98 87.19%
4.33 3 32 0.57 0.18 4.16 91.19% 4.25 4 31.81 0.65 0.21 4.36 95.72%
2.92 5 31.54 0.09 0.03 4.39 96.34% 1.96 6 31.76 0.00003 0.00 4.39
96.34% 1.75 4.68 0.07% 0.003 0.02%
__________________________________________________________________________
See FIG. 15.
Precipitate formed with the phosphoric acid sample after stage 3
and redissolved after the fourth. Precipitate formed with the
sulfuric acid sample after the third stage and redissolved after
the fifth. No precipitate formed at any stage during the
hydrochloric acid run. Each time the precipitate dissolved, a
dramatic decrease in pH was noted.
EXAMPLE 8
A concentrated fermentation broth containing lactic acid (65%) was
acidulated with 75% phosphoric acid to a pH of 3.0. The acidulated
suspension was clarified by filtration and a portion of the
supernatant was subjected to a six by six counter-current
extraction process. (Mass-Transfer Operations, 3rd Ed., Robert E.
Treybal, McGraw-Hill, 1955, p. 518.) The filtered, acidulated
supernatant contained 55.39% lactic acid, 3.27% phosphate, 2.56%
ammonia, and 28.7% water. The supernatant was extracted at a
solvent to aqueous ratio of 4:1; the solvent contained hexanol,
0.7% phosphoric acid, and 7% water.
TABLE 8
__________________________________________________________________________
Counter-Current Extraction of Broth
__________________________________________________________________________
Aqueous Aqueous Solvent Aqueous Solvent Final Aqueous Broth Feed
Solvent In Out out Wt Loss Wt Gain % lactic % PO4 % NH3 % Water %
__________________________________________________________________________
Hexanol Row 1; Stage 1 8.13 32.02 5.62 34.36 2.51 2.34 -- -- -- --
-- 2 5.62 32.06 5.07 32.39 0.55 0.33 -- -- -- -- -- 3 5.07 32.03
5.01 31.89 0.06 -0.14 -- -- -- -- -- 4 5.01 32.00 5.01 31.77 -0.06
-0.23 -- -- -- -- -- 5 5.07 32.02 5.07 31.75 0 -0.27 -- -- -- -- --
6 5.07 32.04 5.07 31.82 0 -0.22 4.08% 18.76% 3.70% 60.70% 0.03% Row
2; Stage 1 7.99 32.39 4.54 35.51 3.45 3.12 -- -- -- -- -- 2 4.54
31.89 4.08 32.08 0.46 0.19 -- -- -- -- -- 3 4.08 31.77 3.97 31.69
0.11 -0.08 -- -- -- -- -- 4 3.97 31.71 4.03 31.44 -0.06 -0.31 -- --
-- -- -- 5 4.03 31.82 4.08 31.58 -0.05 -0.24 -- -- -- -- -- 6 4.08
31.99 4.12 31.75 -0.04 -0.24 5.28% 18.39% 3.71% 59.30% 0.02% Row 3;
Stage 1 8.02 32.08 4.54 35.35 3.48 3.27 -- -- -- -- -- 2 4.54 31.69
3.89 32.13 0.65 0.44 -- -- -- -- -- 3 3.89 31.44 3.70 31.49 0.19
0.05 -- -- -- -- -- 4 3.7 31.58 3.74 31.37 -0.04 -0.21 -- -- -- --
-- 5 3.74 31.75 3.83 31.48 -0.09 -0.27 -- -- -- -- -- 6 3.83 32.03
3.86 31.75 -0.03 -0.28 9.86% 15.01% 3.91% 58.10% 0.05%
__________________________________________________________________________
Final Solvent % lactic % PO4 % NH3 % Water % Hexanol g lactic in g
lactic out Solvent g Lactic Out
__________________________________________________________________________
Aqueous Row 1; Stage 1 7.73% 0.03% 0.07% 5.62% -- 4.503 2.656 -- 2
-- -- -- -- -- -- -- -- 3 -- -- -- -- -- -- -- -- 4 -- -- -- -- --
-- -- -- 5 -- -- -- -- -- -- -- -- 6 -- -- -- -- -- -- -- 0.207 Row
2; Stage 1 10.55% 0.04% 0.13% 6.04% -- 4.426 3.746 -- 2 -- -- -- --
-- -- -- -- 3 -- -- -- -- -- -- -- -- 4 -- -- -- -- -- -- -- -- 5
-- -- -- -- -- -- -- -- 6 -- -- -- -- -- -- -- 0.218 Row 3; Stage 1
10.66% 0.03% 0.12% 6.03% -- 4.442 3.768 -- 2 -- -- -- -- -- -- --
-- 3 -- -- -- -- -- -- -- -- 4 -- -- -- -- -- -- -- -- 5 -- -- --
-- -- -- -- -- 6 -- -- -- -- -- -- -- 0.381
__________________________________________________________________________
Aqueous Aqueous Solvent Aqueous Solvent Final Aqueous Broth Feed
Solvent In Out out Wt Loss Wt Gain % lactic % PO4 % NH3 % Water %
__________________________________________________________________________
Hexanol Row 4; Stage 1 8.02 32.13 4.36 35.59 3.66 3.46 -- -- -- --
-- 2 4.36 31.49 3.72 31.96 0.64 0.47 -- -- -- -- -- 3 3.72 31.37
3.53 31.72 0.19 0.35 -- -- -- -- -- 4 3.53 31.48 3.52 31.3 0.01
-0.18 -- -- -- -- -- 5 3.52 31.75 3.72 31.29 -0.2 -0.46 -- -- -- --
-- 6 3.72 32.05 3.98 31.83 -0.26 -0.22 9.40% 14.42% 3.83% 58.40%
0.03% Row 5; Stage 1 8.00 31.96 4.68 35.09 3.32 3.13 -- -- -- -- --
2 4.68 31.72 3.80 32.07 0.88 0.35 -- -- -- -- -- 3 3.80 31.30 3.77
31.06 0.03 -0.24 -- -- -- -- -- 4 3.77 31.29 3.37 31.25 0.40 -0.04
-- -- -- -- -- 5 3.37 31.83 3.67 31.51 -0.30 -0.32 -- -- -- -- -- 6
3.67 32.08 3.63 31.61 0.04 -0.47 10.16% 14.45% 3.96% 58.00% 0.03%
Row 6; Stage 1 8.02 32.07 4.39 35.49 3.63 3.42 -- -- -- -- -- 2
4.39 31.06 3.85 31.56 0.54 0.5 -- -- -- -- -- 3 3.85 31.25 3.45
31.32 0.40 0.07 -- -- -- -- -- 4 3.45 31.51 3.40 31.42 0.05 -0.09
-- -- -- -- -- 5 3.40 31.61 3.45 31.35 -0.05 -0.26 -- -- -- -- -- 6
3.45 32.02 3.59 31.80 -0.14 -0.22 12.94% 12.13% 4.12% 56.10% 0.03%
__________________________________________________________________________
Final Solvent % lactic % PO4 % NH3 % Water % Hexanol g lactic in g
lactic out Solvent g Lactic Out
__________________________________________________________________________
Aqueous Row 4; Stage 1 11.10% 0.04% 0.16% 6.04% -- 4.442 3.950 -- 2
-- -- -- -- -- -- -- -- 3 -- -- -- -- -- -- -- -- 4 -- -- -- -- --
-- -- -- 5 -- -- -- -- -- -- -- -- 6 -- -- -- -- -- -- -- 0.374 Row
5; Stage 1 10.69% 0.03% 0.14% 5.91% -- 1.430 3.751 -- 2 -- -- -- --
-- -- -- -- 3 -- -- -- -- -- -- -- -- 4 -- -- -- -- -- -- -- -- 5
-- -- -- -- -- -- -- -- 6 -- -- -- -- -- -- -- 0.369 Row 6; Stage 1
11.51% 0.04% 0.36% 6.08% -- 4.441 4.085 --
2 3.58% 0.00% 0.12% 4.55% -- -- -- -- 3 1.79% 0.00% 0.02% 4.43% --
-- -- -- 4 1.08% 0.00% 0.02% 4.75% -- -- -- -- 5 0.68% 0.03% 0.01%
4.71% -- -- -- -- 6 0.74% 0.03% 0.01% 5.06% -- -- -- 0.465
__________________________________________________________________________
EXAMPLE 9
A cross-current extraction was conducted to purify lactic acid. The
organic phase comprised lactic acid 10.81%, water 8.08%, hexanol
78.43%, and phosphate 205 ppm, and the aqueous phase comprised
lactic acid 19.09% and water 80.91%. A 10:1 organic/aqueous ratio
was used.
TABLE 9
__________________________________________________________________________
Cross-Current Lactic Acid Purification Aqueous Layer Analysis % of
g Organic g Organic g Aqueous g Aqueous % mg Phos Total Cum % Stage
# Phase In Phase Out Phase In Phase Out Water % Lactic % Phos
Aqueous Phos Phos
__________________________________________________________________________
Out 1 30.06 30.71 3.07 2.36 72.9 21.04 0.179 4.215 68.40 68.4 2
30.71 30.48 3.01 3.11 75.94 21.38 0.065 2.022 32.81 101.21 3 30.48
30.21 3.02 3.14 76.01 21.29 0.022 0.703 11.41 112.62 4 30.21 29.89
3.08 3.22 76.78 20.61 0.012 0.399 6.48 119.1 5 29.89 29.64 3.03
3.17 77.79 20.73 0.002 0.060 0.98 120.08 6 29.64 29.4 3.02 3.11
77.15 20.31 0.000 0.000 0.00 120.08 7 29.4 29.15 3.07 3.22 76.88
19.89 0.000 0.000 0.00 120.08 8 29.15 28.94 3.13 3.22 77.21 19.82
0.000 0.000 0.00 120.08
__________________________________________________________________________
See FIG. 16.
EXAMPLE 10
To find the optimum aqueous lactic acid concentration for ion
removal from lactic acid in hexanol, single 10:1 solvent/aqueous
extractions were performed with concentrations of 18, 21, 23, 25,
27, and 30% lactic acid in the aqueous phase. The solvent phase was
9.73% lactic acid, 330 ppm PO.sub.4, 9.55% H.sub.2 O, and 76.22%
hexanol.
TABLE 10 ______________________________________ Theoretical Change
in Lactic Aqueous Conc. Actual Aqueous Conc. Acid Conc. in Feed
______________________________________ 18% 18.69% -1.37% 21% 22.01%
+1.37% 23% 22.01% +6.16% 25% 24.47% +7.85% 27% 28.71% +10.96% 30%
31.60% +12.29% ______________________________________
Using a best fit curve (see FIG. 17), 19% aqueous lactic acid
should give little or no movement of lactic acid from solvent to
aqueous phase during purification/ion removal.
EXAMPLE 11
The effect of temperature on the back extraction of lactic acid
from hexanol to water was tested. The original single phase in this
experiment contained 18.31% (weight) lactic acid, 12.70% water, and
68.99% hexanol. Water was added at 20.degree. C., 30.degree. C.,
and 45.degree. C.
TABLE 11 ______________________________________ 20.degree. C.
30.degree. C. 45.degree. C. ______________________________________
single phase (g) 10.71 11.18 10.85 water added to reach 0.3 0.32
0.39 cloud point (g) water excess (g) 1.0 1.3 1.3 Total (g) 12.01
12.80 12.54 ______________________________________
TABLE 12 ______________________________________ quantity of phases
(measured) 20.degree. C. 30.degree. C. 45.degree. C.
______________________________________ aqueous (g) 1.61 1.71 1.59
organic (g) 10.59 10.86 10.55
______________________________________
TABLE 13 ______________________________________ Analysis of Phases
Aqueous Organic % % % % % K.sub.s * lactic hex. water lactic % hex.
water lactic ______________________________________ 20.degree. C.
27.29 3.76 68.95 14.19 72.93 12.88 0.520 30.degree. C. 27.27 4.33
68.40 14.70 72.33 12.97 0.539 45.degree. C. 26.90 4.13 68.97 14.63
72.36 13.01 0.544 aver- 27.15 4.07 68.78 14.51 72.52 12.95 0.534
age ______________________________________ *K.sub.2 = distribution
coefficient = c.sub.s /c.sub.w, where c.sub.s = concentration of
lactic acid in aqueous phase and c.sub.w = concentration of lactic
acid in solvent phase.
TABLE 14 ______________________________________ Total Composition %
lactic % hexanol % water ______________________________________
20.degree. C. 15.85 63.88 20.28 30.degree. C. 16.05 63.34 20.61
45.degree. C. 16.23 63.43 20.35
______________________________________
Thus, there appeared to be no benefit in extraction efficiency from
increasing the extraction temperature from 20.degree. C. to
45.degree. C. To the extent any trend could be discerned,
increasing temperature appeared to have an adverse effect.
EXAMPLE 12
First stage back extractions were performed on a lactic acid
solution (11.95% lactic acid, 10.3% water, and 77.75% hexanol) with
water at 4:1, 6:1, 8:1, and 10:1 organic to aqueous ratios. The
lactic acid concentration was measured in the aqueous phase and the
percent lactic acid removal was calculated for each of the various
ratios of organic to aqueous phase. From this recovery, an
estimation of the number of stages required to remove 97% of the
lactic acid was made. Ratios of 4:1, 6:1, and 8:1 require 6, 9, and
11 stages respectively.
TABLE 15A
__________________________________________________________________________
g solvent % aqueous % aqueous % lactic solvent lactic solvent in g
lactic g water g aqueous out g solvent out lactic lactic removal
__________________________________________________________________________
4:1 4 11.95% 0.48 1 1.35 3.65 14.28% 0.193 40.33% 6:1 6.01 11.95%
0.72 1 1.4 5.58 16.07% 0.225 31.33% 8:1 8 11.95% 0.96 1.01 1.43 7.6
17.64% 0.252 26.39% 10:1 10 11.95% 1.20 1.01 1.53 9.49 18.34% 0.281
23.48%
__________________________________________________________________________
TABLE 15B ______________________________________ g g % 4:1 lactic
lactic removed extraction g lactic % removal removed cum cum
______________________________________ 1 0.478 40.33% 0.193 0.193
40.38% 2 0.285 40.33% 0.115 0.308 64.42% 3 0.170 40.33% 0.069 0.377
78.77% 4 0.101 40.33% 0.041 0.417 87.33% 5 0.061 40.33% 0.024 0.442
92.44% 6 0.036 40.33% 0.015 0.456 95.49%
______________________________________
TABLE 15C ______________________________________ g g % 6:1 lactic
lactic removed extraction g lactic % removal removed cum cum
______________________________________ 1 0.718 31.33% 0.225 0.225
31.34% 2 0.493 31.33% 0.155 0.380 52.86% 3 0.339 31.33% 0.106 0.486
67.63% 4 0.233 31.33% 0.073 0.558 77.78% 5 0.160 31.33% 0.050 0.609
84.75% 6 0.110 31.33% 0.034 0.643 89.54% 7 0.075 31.33% 0.024 0.666
92.82% 8 0.052 31.33% 0.016 0.683 95.08% 9 0.036 31.33% 0.011 0.694
96.63% ______________________________________
TABLE 15D ______________________________________ g g % 8:1 lactic
lactic removed extraction g lactic % removal removed cum cum
______________________________________ 1 0.956 26.39% 0.252 0.252
26.36% 2 0.704 26.39% 0.186 0.438 45.79% 3 0.518 26.39% 0.137 0.574
60.08% 4 0.381 26.39% 0.101 0.675 70.61% 5 0.281 26.39% 0.074 0.749
78.36% 6 0.207 26.39% 0.055 0.804 84.06% 7 0.152 26.39% 0.040 0.844
88.26% 8 0.112 26.39% 0.030 0.873 91.35% 9 0.082 26.39% 0.022 0.895
93.62% 10 0.061 26.39% 0.016 0.911 95.30% 11 0.045 26.39% 0.012
0.923 96.53% ______________________________________
See FIG. 18.
EXAMPLE 12
A cross-current six-stage back extraction was performed with a 4:1
solvent to aqueous ratio. The solvent composition was 10.82% lactic
acid, 10.5% water, and 78.68% hexanol. 98.62% of the lactic acid
was recovered in the aqueous stream. See FIG. 19.
EXAMPLE 14
A counter-current six-stage back extraction was performed with a
4:1 solvent to aqueous ratio. The solvent comprised 10.5% water,
10.82% lactic acid, and 78.62% hexanol. 16.04% of the lactic acid
entering row 6 was left with the solvent stream. The final aqueous
stream comprised 20.06% lactic acid and 0.7% hexanol. The final
solvent stream comprised 2.03% lactic acid and 7.83% water.
The preceding description of specific embodiments of the present
invention is not intended to be a complete list of every possible
embodiment of the invention. Persons who are skilled in this field
will recognize that modifications can be made to the specific
embodiments described here that would be within the scope of the
present invention.
* * * * *